Swansea rejected a bid from Forest for Pratley in August 2010, but a career-best return of 10 league goals from 28 starts last season caught the attention of Bolton, Wigan Athletic and Newcastle United.

"It's been a difficult decision for me and my family to make because Swansea is a fantastic club with such friendly and passionate supporters," said Pratley.

My goal in the play-off semi-final in front of the Swansea fans was a nice way to finish at the Liberty

Darren Pratley

"It's not going to be easy for me, but if there was a good time to leave then it's now with the club having secured their place in the Premier League.

"I hope people feel I have contributed to that rise from League One and my goal in the play-off semi-final in front of the Swansea fans was a nice way to finish at the Liberty.

"I wish the club, the players and the supporters the very best of luck in the Premier League and they will always be in my heart.''

Swansea chairman Jenkins, who is in contract talks with goalkeeper Dorus de Vries and defender Angel Rangel, paid tribute to Pratley's contribution.

"As a club we would like to thank Darren for his services over the last five years,'' Jenkins said. "He has played a key part in our success over the years and while we are sorry to see him go we wish him every success in his new challenge.

"He has always been a good professional and the door will always be open with a warm welcome awaiting him at Swansea City.''